The invention relates to an electromagnetic patterning system of the class defined in the generic part of claim 1.
Patterning systems of this kind operate on the principle of using electromagnetic means to shift or swing the control elements associated individually with the knitting tools into one of at least two positions in accordance with a pattern. This process, referred to as "sorting the control elements," is necessary in order to bring the knitting tools at a later point in time, and in relation to the position of the control elements, into a knit or missknit position, for example. To avoid having to provide each individual control element with its own electromagnetic patterning system, it is common practice to provide only one patterning system on each knitting system of the knitting machine and to perform the sorting of the control elements either by moving the control elements past the parts of the patterning system which produce the sorting, or, vice versa, by moving the parts which produce the sorting past the control elements. This relative movement is produced, for example, by the rotation of the needle cylinder of a circular knitting machine or the motion of the slide of a flat knitting machine.
There are essentially two possibilities for performing the sorting. The one possibility (German Fed. Pat. 12 69 762) consists in performing the swinging or shifting of the control elements by purely electromagnetic means. This is accomplished, for example, by providing an electromagnetic control pole with a pole face disposed transversely of the direction of the relative movement, which leaves the control elements that run past it either in their current position or pulls them by a defined, even through small amount, to a position different from their current position. According to the other possibility (German Fed. Pat. 15 85 211), however, the shift or swing of the control elements is achieved by mechanical means, for example in that a resiliently biased spring rod is either held by magnetic force or swung by sprung force in the area of the control pole.
These and all comparable electromagnetic patterning system have it in common that the sorting of the control elements i.e., their shifting or swinging to one of the two positions, must take place while the control elements are moving past the control pole. As a rule, holding poles are also provided which follow the control pole in the direction of movement, but their purpose is only to intensify the sorting started in the area of the control poles, i.e., to increase the distances between the control elements in the one or the other position. It follows that the electrical signals fed to the control poles must last at least long enough for the control elements to be shifted or swung by the necessary amount, and that the reliability of the sorting is all the poorer as the relative velocity between the control elements and the control poles is greater and the distance between the individual control elements is smaller. Moreover, control or holding poles with comparatively greater power are needed, and this is undesirable not only for reasons of power consumption, but also because it results in the danger that the control or holding poles will act not only on the control element that is to be selected but also on at least one adjacent control element, thereby impairing reliability of operation.
It is the object of the invention to improve the patterning system of the kind defined above such that it will operate faster, be less liable to trouble, and operate with less powerful control poles or holding poles.
This is to be achieved by making the duration of the excitation of the control poles independent of the swinging or shifting movements of the control elements.